| 词条 | Hypomanganate |
| 释义 |
In chemistry, hypomanganate, also called manganate(V) or tetraoxidomanganate(3−), is a trivalent anion (negative ion) composed of manganese and oxygen, with formula {{chem|MnO|4|3-}}. Hypomanganates are usually bright blue.[1][1] Potassium hypomanganate {{chem|K|3|MnO|4}} is the best known salt, but sodium hypomanganate {{chem|Na|3|MnO|4|}}, barium hypomanganate {{chem|Ba|3|(|MnO|4|)|2}}, and the mixed potassium-barium salt {{chem|KBaMnO|4}} is also known.[3] The anion can replace phosphate {{chem|PO|4|3-}} in synthetic variants of the minerals apatite[2][3] and brownmillerite.[4] HistoryThe manganate(V) anion was first reported in 1946 by Hermann Lux, who synthesized the intensely blue sodium hypomanganate by reacting sodium oxide {{chem|Na|2|O}} and manganese dioxide {{chem|MnO|2}} in fused sodium nitrite {{chem|NaNO|2}} at 500 °C.[5][3] He also crystalized the salt from strong (50%) sodium hydroxide solutions as the decahydrate {{chem|Na|3|MnO|4}}·10{{chem|H|2|O}}. Structure and propertiesManganate(V) is a tetrahedral oxyanion structurally similar to sulfate, manganate, and permanganate. As expected for a tetrahedral complex with a d2 configuration, the anion has a triplet ground state.[6] The anion is a bright blue species[7] with a visible absorption maximum at wavelength λmax = 670 nm (ε = {{nowrap|900 dm3 mol−1 cm−1}}).[8][9] StabilityHypomanganate is unstable towards disproportionation to manganate(VI) and manganese dioxide:[10][7] The estimated electrode potentials at pH 14 are:[11][12][13] MnO{{su|b=4|p=2−}} + e− {{eqm}} MnO{{su|b=4|p=3−}} E = +0.27 V MnO{{su|b=4|p=3−}} + e− + {{nowrap|2 H2O}} {{eqm}} MnO2 + {{nowrap|4 OH−}} E = +0.96 V However, the reaction is slow in very alkaline solutions (with OH− concentration above 5–10 mol/L.[7][5] The disproportionation is believed to pass through a protonated intermediate,[13] with the acid dissociation constant for the reaction HMnO{{su|b=4|p=2−}} {{eqm}} MnO{{su|b=4|p=3−}} + H+ being estimated as pKa = {{nowrap|13.7 ± 0.2}}.[14] However, K3MnO4 has been cocrystallized with Ca2Cl(PO4), allowing the study of the UV–visible spectrum of the hypomanganate ion.[10][15] PreparationHypomanganates may be prepared by the careful reduction of manganates with sulfite,[7] hydrogen peroxide[16] or mandelate.[9] Hypomanganates can also be prepared by the solid state method under O2 flow near 1000 °C[6][2][3] [4] They can be prepared also via low temperature routes such as hydrothermal synthesis or flux growth.[6] UsesThe strontium vanadate fluoride {{chem|Sr|5|(|VO|4|)|3|F}} compound, with hypomanganate substituted for some vanadate units, has been investigated for potential use in near infrared lasers.[17] The barium salt {{chem|Ba|3|(|MnO|4|)|2}} has interesting magnetic properties.[18] Related compoundsIn theory, hypomanganate would be the conjugate base of hypomanganic acid {{chem|H|3|MnO|4}}. This acid cannot be formed because of its rapid disproportionation, but its third acid dissociation constant has been estimated by pulse radiolysis techniques:[14] HMnO{{su|b=4|p=2−}} {{eqm}} MnO{{su|b=4|p=3−}} + H+ pKa = {{nowrap|13.7 ± 0.2}} Cyclic esters of hypomanganic acid are thought to be intermediates in the oxidation of alkenes by permanganate.[9] See also
References1. ^D. Reinen, W. Rauw, U. Kesper, M. Atanasov, H. U Güdel, M. Hazenkamp, and U. Oetliker (1997): "Colour, luminescence and bonding properties of tetrahedrally coordinated chromium(IV), manganese(V) and iron(VI) in various oxide ceramics" Journal of Alloys and Compounds, volume 246, issue 1-2, pages 193-208. {{doi|10.1016/S0925-8388(96)02461-9}} 2. ^1 K. Dardenne, D. Vivien, and D. Huguenin (1999): "Color of Mn(V)-substituted apatites A10((B, Mn)O4)6F2, A = Ba, Sr, Ca; B= P, V". Journal of Solid State Chem.istry, volume 146, issue 2, pages 464-472. {{doi|10.1006/jssc.1999.8394}} 3. ^1 Grisafe, D.A. and Hummel, F.A. (1970): "Pentavalent ion substitutions in the apatite structure, part A: Crystal chemistry". Journal of Solid State Chemistry, volume 2, issue 2, pages 160-166 {{doi|10.1016/0022-4596(70)90064-2}} 4. ^1 P. Jiang, J. Li, A. Ozarowski, A. W. Sleight, and M. A, Subramanian (2013): "Intense turquoise and green colors in brownmillerite-type oxides based on Mn5+ in {{chem|Ba|2|In|2-x|Mn|x|O|5+x}}" Inorganic Chemistry, volume 52, issue 3, pages 1349-1357. {{doi|10.1021/ic3020332}} 5. ^1 Herrman Lux (1946): "Über Salze des fünfwertigen Mangans." Zeitschrift für Naturforschung, volume 1, pages 281-283. 6. ^1 2 3 4 {{cite journal|authors=zur Loye, K. D.; Chance, W. M.; Yeon, J.; zur Loye, H.-C.|title=Synthesis, Crystal Structure, and Magnetic Properties of the Oxometallates KBaMnO4 and KBaAsO4|journal=Solid State Sciences|year=2014|volume=37|pages=86-90|doi=10.1016/j.solidstatesciences.2014.08.013}} 7. ^1 2 3 4 {{Greenwood&Earnshaw1st|pages=1221–22}}. 8. ^{{citation | journal = J. Chem. Soc. | year = 1956 | pages = 3373–80 | doi = 10.1039/JR9560003373 | title = Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions | first1 = A. | last1 = Carrington | first2 = M. C. R. | last2 = Symons}} 9. ^1 2 {{citation | title = Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1993 | volume = 115 | issue = 24 | pages = 11231–36 | doi = 10.1021/ja00077a023}}. 10. ^1 {{Cotton&Wilkinson4th|page=746}}. 11. ^{{RubberBible62nd|page=D-134}}. 12. ^{{citation | title = Manganese – compounds – standard reduction potentials | url = http://www.webelements.com/manganese/compounds.html | publisher = WebElements | accessdate = 2010-06-26}}. 13. ^1 {{citation | title = Rate of the MnO4−/MnO42− and MnO42−/MnO43− electrode reactions in alkaline solutions at solid electrodes | first1 = K. | last1 = Sekula-Brzezińska | first2 = P. K. | last2 = Wrona | first3 = Z. | last3 = Galus | journal = Electrochim. Acta | volume = 24 | issue = 5 | pages = 555–63 | doi = 10.1016/0013-4686(79)85032-X | year = 1979}}. 14. ^1 {{citation | title = Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms | first1 = J. D. | last1 = Rush | first2 = B. H. J. | last2 = Bielski | journal = Inorg. Chem. | year = 1995 | volume = 34 | issue = 23 | pages = 5832–38 | doi = 10.1021/ic00127a022}}. 15. ^{{citation | journal = J. Chem. Soc. | year = 1956 | pages = 3373–80 | doi = 10.1039/JR9560003373 | title = Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions | first1 = A. | last1 = Carrington | first2 = M. C. R. | last2 = Symons}}. 16. ^{{citation | title = Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds | first1 = Donald G. | last1 = Lee | first2 = Tao | last2 = Chen | journal = J. Am. Chem. Soc. | year = 1989 | volume = 111 | issue = 19 | pages = 7534–38 | doi = 10.1021/ja00201a039}}. 17. ^L. D. Merkle, Y. Guyot, and B. H. T. Chai (1995): "Spectroscopic and laser investigations of Mn5+:Sr5(VO4)3F". Journal of Applied Physics, volume 77, issue 2, pages 474-480. {{doi|10.1063/1.359585}} 18. ^M. B. Stone, M. D. Lumsden, Y. Qiu, E. C. Samulon, C. D. Batista, and I. R. Fisher (2008): "Dispersive magnetic excitations in the S=1 antiferromagnet {{chem|Ba|3|Mn|2|O|8}}". Physics Review B, volume 77, page 134406 {{doi|10.1103/PhysRevB.77.134406}} 2 : Manganese compounds|Transition metal oxyanions |
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